Fluid dispensing assemblies generally include structures to take the fluid into the assembly or store it locally, route it to the appropriate output port, an actuator to selectively cause the fluid to exit the output port, and control circuit to control the selection and activation of the actuator. In some instances, the structures to route the ink to the output port and structures upon which the actuators operate may be contained in a fluid dispensing subassembly.
One such fluid dispensing assembly consists of a print head, either for liquid ink or solid inks that are melted. It is generally helpful to have a specific example to understand aspects of the discussion, but no limitation to a print head is intended or should be implied. In the print head example, the fluid dispensing subassembly typically consists of series of metal plates, brazed or otherwise bonded together. For purposes of the discussion here, the jet stack will be considered to consist of at least the membrane upon which the actuators operate, at least one ‘body’ plate, the term ‘body’ applying to any plate between the membrane and the nozzle plate, and the nozzle plate that contains the exit ports.
In some instances, print heads include the ink manifolds that store and dispense the ink local to the jet stack. To achieve high density, it is advantageous to remove these internal manifolds. The fluid dispensing assembly still requires some means to transfer ink from an ink reservoir to the output ports.
Ideally, this transfer would occur through a single port for each nozzle in the nozzle plate, for the printhead example, or more generally for each output port. This results in a large number of ‘vertical’ ports that must pass through multiple layers and maintain alignment. The layers may include the diaphragm or other structure upon which the actuator operates, between the actuators, through any standoffs or insulators, a circuit board for the control circuitry and any heaters needed, such as in solid ink printers. The small dimensions of these inlets make it very difficult to assemble these layers without misalignment, and to maintain uniform fluid characteristics in the presence of any misalignment.